Newbie here and not sure which section to put this question in so apologies if i'm in 'the wrong one'!!

I have an LG RHT-497H DVD recorder and been trying to offload files from the HD to a flash drive via the USB port. I looked in the instruction manual but found nothing relating to this other than a diagram of the front controls showing where the USB port is.

What johns0 said, plus to add that DVD recorders usually if not always encrypt what they record specifically to prevent you from doing what you propose. The manufacturers had to agree to this to placate Hollywood. Hollywood can't legally stop you from having DVD recorders or DVRs but they certainly can legally make it damn near impossible for you to directly copy the recorded contents off any hard drives those devices use for video storage.